Motives could be these:

Military – We needed to protect what we deemed to be vital interests of the United States and put our military into action to assure our ability to access this interest.

Market – We had a product or products to sell, and since we could not gain an access through normal means we forced our way into a market country or region and undercut prices to sell our product.

Materials – We needed more raw materials to continue creating products. If we can force a country to sell us the needed raw materials out of fear of our military, we are being imperialistic.

Sites for reason for imperialism

http://www.socialstudieshelp.com/Lesson_58_Notes.htm

http://www.wsu.edu:8080/~wldciv/world_civ_reader/world_civ_reader_2/kipling.html

http://www.socialstudieshelp.com/Lesson_59_Notes.htm Includes cartoon

http://www.socialstudieshelp.com/USRA_Imperialism_Justify.htm

Events Associated with Imperialism

http://mentorhigh.com/roberts/APUS/APUSHP8/APUSQuestEmpireHP8.html

http://www.hartford-hwp.com/archives/45/046.html

http://www.u-s-history.com/pages/h1049.html

http://www.u-s-history.com/pages/h940.html

http://mentorhigh.com/roberts/APUS/APUSHP10/APUSForAffChartHP10.html

http://www.socialstudieshelp.com/Lesson_64_Notes.htm

http://www.smplanet.com/imperialism/toc.html

http://www.factmonster.com/ipka/A0762461.html

http://us.history.wisc.edu/hist102/photos/html/1084.html

http://www.regentsprep.org/Regents/global/themes/imperialism/southamerica.cfm

http://www.socialstudieshelp.com/USRA_Foreign_Policy.htm

http://www.neravt.com/left/invade.htm

The events involving the US and imperialism took place in Latin America and Asia. Since you are doing a power point presentation I suggest that you use charts, maps and cartoons as part of your presentation.

Good luck.